#Make code wrap text so it doesn't go off the page when Knitting to PDF
library(knitr)
opts_chunk$set(tidy.opts=list(width.cutoff=60),tidy=TRUE)
Click here to navigate to the version-tracked reproducible manuscript (.Rmd file)
Great-tailed grackles (Quiscalus mexicanus) are known to have a mating system where females are the sole builders of the nest and caretakers of the young (Johnson et al. (2000)). However, there is one report from Selander (1970) in which an unmarked male great-tailed grackle provided parental care to two juveniles in Austin, Texas. Here, we report repeated parental care events by multiple individually marked adult males in a population of great-tailed grackles in Tempe, Arizona. We also report male parental care by unmarked adult males in Tempe, Arizona; Santa Barbara, California; and San Clemente, California. We then propose to begin to investigate hypotheses determining whether male parental care 1) is associated with hormone profiles (testosterone, estrogen, prolactin, progesterone) potentially because hormones mediate investment in competition and care behavior; 2) increases the number of offspring that survive to independence; 3) is a local adaptation, unique to specific populations where it has evolved; and 4) is a mating strategy.
This preregistration was written (Jun 2019) when an individually marked male provided repeated parental care in Tempe, Arizona, at which point behavioral data collection began. We submitted it to Peer Community in Ecology for pre-study peer review (Dec 2019) before collecting data from subsequent breeding seasons and before analyzing any of the data involved in hypothesis testing.
We may publish the anecdotes and the results from hypotheses separately.
Chile, an adult male great-tailed grackle, was color-marked with bands on 24 April 2018 at the Arizona State University (ASU) campus in Tempe, Arizona. On 02 June 2019, Folsom observed Chile providing parental care for two fledglings (both were greater than 23 days of age because they were capable of flying (Skutch (1954))). The larger fledgling lacked feathers around its eyes, while the smaller fledgling had feathers around its eyes, indicating it was older than the larger fledgling (Skutch (1954)). Based on their development, the smaller but older fledgling was likely female, while the other was likely a male because adult female grackles are typically much smaller than adult males (Selander (1958)).